Aluminum conductor composite core reinforced cable and method of manufacture

ABSTRACT

This invention relates to an aluminum conductor composite core reinforced cable (ACCC) and method of manufacture. An ACCC cable having a composite core surrounded by at least one layer of aluminum conductor. The composite core comprises at least one longitudinally oriented substantially continuous reinforced fiber type in a thermosetting resin matrix having an operating temperature capability within the range of about 90 to about 230° C., at least 50% fiber volume fraction, a tensile strength in the range of about 160 to about 240 Ksi, a modulus of elasticity in the range of about 7 to about 30 Msi and a thermal expansion coefficient in the range of about 0 to about 6×10 −6  m/m/C. According to the invention, a B-stage forming process may be used to form the composite core at improved speeds over pultrusion processes wherein the speeds ranges from about 9 ft/min to about 50 ft/min.

CLAIM FOR PRIORITY

In relation to this International Application, applicants claim priorityof earlier U.S. provisional application Ser. No. 60/374,879 filed in theUnited States Patent and Trademark Office on 23 Apr. 2002, the entiredisclosure of which is incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to an aluminum conductor composite core(ACCC) reinforced cable and method of manufacture. More particularly, toa cable for providing electrical power having a reinforced fiberthermosetting resin composite core surrounded by aluminum conductorcapable of carrying increased ampacity at elevated temperatures.

BACKGROUND OF INVENTION

This invention relates to composite core members and aluminum conductorcomposite core (ACCC) reinforced cable products made therefrom. Thisinvention further relates to a forming process for an aluminum conductorcomposite core reinforced cable (ACCC). In the traditional aluminumconductor steel reinforced cable (ACSR) the aluminum conductor transmitsthe power and the steel core is designed to carry the transfer load.

In an ACCC cable, the steel core of the ACSR cable is replaced by acomposite core comprising at least one reinforced fiber type in athermosetting resin matrix. Replacing the steel core has manyadvantages. An ACCC cable can maintain operating temperatures in therange of about 90 to about 230° C. without corresponding sag induced intraditional ACSR cables. Moreover, to increase ampacity, an ACCC cablecouples a higher modulus of elasticity with a lower coefficient ofthermal expansion.

This invention relates to an aluminum conductor composite corereinforced cable suitable for operation at high operating temperatureswithout being limited by current operating limitations inherent in othercables for providing electrical power wherein provision of electricalpower includes both distribution and transmission cables. Typical ACSRcables can be operated at temperatures up to 100° C. on a continuousbasis without any significant change in the conductor's physicalproperties related to a reduction in tensile strength. These temperaturelimits constrain the thermal rating of a typical 230-kV line, strungwith 795 kcmil ACSR “Drake” conductor, to about 400 MVA, correspondingto a current of 1000 A.

Conductor cables are constrained by the inherent physicalcharacteristics of the components that limit ampacity. Morespecifically, the ampacity is a measure of the ability to send powerthrough the cable wherein increased power causes an increase in theconductor's operating temperature. Excessive heat causes the cable tosag below permissible levels. Therefore, to increase the load carryingcapacity of transmission cables, the cable itself must be designed usingcomponents having inherent properties that withstand increased ampacitywithout inducing excessive sag.

Although ampacity gains can be obtained by increasing the conductor areathat wraps the core of the transmission cable, increasing conductorweight increases the weight of the cable and contributes to sag.Moreover, the increased weight requires the cable to use increasedtension in the cable support infrastructure. Such large load increasestypically would require structure reinforcement or replacement, whereinsuch infrastructure modifications are typically not financiallyfeasible. Thus, there is financial motivation to increase the loadcapacity on electrical transmission cables while using the existingtransmission liens.

European Patent Application No. EP1168374A3 discloses a composite corecomprised of a single type of reinforced glass fiber and thermoplasticresin. The object is to provide an electrical transmission cable whichutilizes a reinforced plastic composite core as a load bearing elementin the cable and to provide a method of carrying electrical currentthrough an electrical transmission cable which utilizes an innerreinforced plastic core. The composite core fails in these objectives. Aone fiber system comprising glass fiber does have the required stiffnessto attract transfer load and keep the cable from sagging. Secondly, acomposite core comprising glass fiber and thermoplastic resin does notmeet the operating temperatures required for increased ampacity, namely,between 90 and 230° C.

Composite cores designed using a carbon epoxy composite core also haveinherent difficulties. The carbon epoxy core has very limitedflexibility and is cost prohibitive. The cable product having a carbonepoxy core does not have sufficient flexibility to permit winding andtransport. Moreover, the cost for carbon fibers are expensive comparedto other available fibers. The cost for carbon fibers is in the range of$5 to $37 per pound compared to glass fibers in the range of $0.36 to$1.20 per pound. Accordingly, a composite core constructed of onlycarbon fibers is not financially feasible.

Physical properties of composite cores are further limited by processingmethods. Previous processing methods cannot achieve a high fiber/resinratio by volume or weight. These processes do not allow for creation ofa fiber rich core that will achieve the strength to compete with a steelcore. Moreover, the processing speed of previous processing methods arelimited by inherent characteristics of the process itself. For example,traditional pultrusion dies are approximately 36 inches, having aconstant cross section. The result is increased friction between thecomposite and the die slowing processing time. The processing times insuch systems for epoxy resins range within about 6 inches/minute toabout 12 inches/minute, which is not economically feasible. Moreover,these processes do not allow for composite configuration and tuningduring the process, wherein tuning comprises changing the fiber/resinratio.

It is therefore desirable to design economically feasible ACCC cableshaving at least one reinforced fiber type in a thermosetting resinmatrix comprising inherent physical characteristics that facilitateincreased ampacity without corresponding cable sag. It is furtherdesirable to process composite cores using a process that allowsconfiguration and tuning of the composite cores during processing andallows for processing at speeds in the range of about 9 ft/min to 50ft/min.

SUMMARY OF THE INVENTION

Increased ampacity can be achieved by using an aluminum conductorcomposite core (ACCC) reinforced cable. An ACCC reinforced cable is ahigh-temperature, low-sag conductor, which can be operated attemperatures above 100° C. while exhibiting stable tensile strength andcreep elongation properties. It is further desirable to achievepractical temperature limits of up to 230° C. Using an ACCC reinforcedcable, which has the same diameter as the original, at 180° C. alsoincreases the line rating by 50% without any significant change instructure loads. If the replacement conductor has a lower thermalelongation rate than the original, then the support structures will nothave to be raised or reinforced.

In particular, replacing the core of distribution and transmissionconductor cables with a composite strength member comprising fiber andresin with a relatively high modulus of elasticity and a relatively lowcoefficient of thermal expansion facilitates an increased conductorcable ampacity. It is further desirable to design composite cores havinglong term durability allowing the composite strength member to operateat least sixty years, and more preferably seventy years at thetemperatures associated with the increased ampacity, about 90 to 230°C., without having to increase either the diameter of the compositecore, or the outside diameter of the conductor. This in turn allows formore physical space to put more aluminum and for the mechanical andphysical performance to be able to meet the sag limits without increasedconductor weight.

Further, the invention allows for formation of a composite core having asmaller core size. A smaller core size allows the conductor cable toaccommodate an increased volume of aluminum wherein an ACCC cable hasthe same strength and weight characteristics as a conductor cablewithout a composite core.

To achieve the desired ampacity gains, a composite core according to theinvention may also combine fibers having a low modulus of elasticitywith fibers having a high modulus of elasticity for increased stiffnessof the core and a lower elongation percent. By combining fibers, a newproperty set including different modulus of elasticity, thermalexpansion, density and cost is obtained. Sag versus temperaturecalculations show achievable ampacity gains when an advanced compositeis combined with low modulus reinforced fibers having inherent physicalproperties within the same range as glassfiber.

Composite cores according to the invention meet certain physicalcharacteristics dependent upon the selection of reinforced fiber typesand thermosetting resins with desired inherent physical properties.Composite cores according to the invention have substantially lowthermal expansion coefficients, substantially high tensile strength,ability to withstand a substantially high range of operatingtemperatures, ability to withstand a low range of ambient temperatures,substantially high dielectric properties and sufficient flexibility topermit winding. In particular, composite cores according to the presentinvention have a tensile strength within the range of about 160 to about240 Ksi, a modulus of elasticity within the range of about 7 to about 30Msi, an operating temperature within the range of about 90 to about 230°C. and a thermal expansion coefficient within the range of about 0 toabout 6×10⁻⁶ m/m/C. These ranges can be achieved by a single reinforcedfiber type or a combination of reinforced fiber types. Theoretically,although the characteristics could be achieved by a single fiber typealone, from a practical point of view, most cores within the scope ofthis invention comprise two or more distinct reinforced fiber types. Inaddition, depending on the physical characteristics desired in the finalcomposite core, the composite core accommodates variations in therelative amounts of fibers.

Composite cores of the present invention can be formed by a B-stageforming process wherein fibers are wetted with resin and continuouslypulled through a plurality of zones within the process. The B-stageforming process relates generally to the manufacture of composite coremembers and relates specifically to an improved apparatus and processfor making resin impregnated fiber composite core members. Morespecifically, according to a preferred embodiment, a multi-phase B-stageprocess forms a composite core member from fiber and resin with superiorstrength, higher ampacity, lower electrical resistance and lighterweight than previous core members. The process enables formation ofcomposite core members having a fiber to resin ratio that maximizes thestrength of the composite, specifically flexural, compressive andtensile strength. In a further embodiment, the composite core member iswrapped with high conductivity aluminum resulting in an ACCC cablehaving high strength and high stiffness characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention are best understood byreferring to the detailed description of the invention, read in light ofthe accompanying drawings, in which:

FIG. 1 is a schematic diagram of a B-stage forming process used forforming reinforced fiber composite core members in accordance with thepresent invention.

FIG. 2 is a schematic diagram of a bushing showing sufficiently spacedpassageways for insertion of the fibers in a predetermined pattern toguide the fibers through the B-stage forming process in accordance withthe present invention.

FIG. 3 is a schematic view of the structure of a bushing, said viewshowing the passageways used to shape and compress the bundles ofreinforced fibers in accordance with the present invention.

FIG. 4 is schematic comparison of two different bushings showing areduction in the passageways from one bushing to the next to shape andcompact the fibers into bundles in forming the composite core inaccordance with the present invention.

FIG. 5 shows a cross-sectional view of thirty possible composite corecross-section geometries according to the invention.

FIG. 6 is a multi-dimensional cross-sectional view of a plurality ofbushings overlaid on top of one another showing the decreasingpassageway size with respective bushings.

FIG. 7 is a multi-phase schematic view of a plurality of bushingsshowing migration of the passageways and diminishing size of thepassageways with each successive bushing in accordance with theinvention.

FIG. 8 is a cross sectional view of one embodiment of a composite coreaccording to the invention.

FIG. 9 is a schematic view of an oven process having cross circular airflow to keep the air temperature constant in accordance with theinvention.

FIG. 10 is a cross-sectional view of the heating element in the ovenrepresented in FIG. 9 showing each heater in the heating element inaccordance with the invention.

FIG. 11 is a schematic view of one embodiment of an aluminum conductorcomposite core (ACCC) reinforced cable showing an inner advancedcomposite core and an outer low modulus core surrounded by two layers ofaluminum conductor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat the disclosure will fully convey the scope of the invention tothose skilled in the art. Like numbers refer to like elementsthroughout. The drawings are not necessarily drawn to scale but areconfigured to clearly illustrate the invention.

The present invention relates to a reinforced composite core member madefrom reinforced fibers embedded in a high temperature resin for use inaluminum conductor composite core reinforced (ACCC) cables to providefor electrical power distribution wherein electrical power distributionincludes distribution and transmission cables. FIG. 11 illustrates atypical embodiment of an ACCC reinforced cable 300. FIG. 11 illustratesan ACCC reinforced cable having a reinforced carbon fiber/epoxy resincomposite inner core 302 and a reinforced glass fiber/epoxy resincomposite outer core 304, surrounded by a first layer of aluminumconductor 306 wherein a plurality of trapezoidal shaped aluminum strandswrap around the composite core and having a second layer of aluminumconductor 308 wherein a plurality of trapezoidal shaped aluminum strandswrap around the first aluminum layer 306.

Composite cores of the present invention comprise the followingcharacteristics: at least one type of reinforced fiber, variablerelative amounts of each reinforced fiber type, reinforced fiber typesof substantially small diameter, reinforced fiber types of asubstantially continuous length, composite cores having a high packingdensity, reinforced fiber tows having relative spacing within thepacking density, a volume fraction at least 50%, a fiber weight fractionbetween about 60 and about 75%, adjustable volume fraction,substantially low thermal expansion coefficient, a substantially hightensile strength, ability to withstand a substantially high range ofoperating temperatures, ability to withstand substantially low ambienttemperature, having the potential to customize composite core resinproperties, substantially high dielectric properties, having thepotential of a plurality of geometric cross section configurations, andsufficient flexibility to permit winding of continuous lengths ofcomposite core.

A composite core of the following invention has a tensile strength inthe range of about 160 to about 240 Ksi, a modulus of elasticity in therange of about 7 to about 30 Msi, an operating temperature in the rangeof about 90 to about 230° C. and a thermal expansion coefficient in therange of about 0 to about 6×10⁻⁶ m/m/C. To achieve these physicalcharacteristics, composite cores of the present invention can compriseone type of reinforced fiber having inherent physical properties toenable the composite core to meet the required physical specifications.From a practical point of view, most cables within the scope of thisinvention comprise at least two distinct reinforced fiber types.

Combining two or more reinforced fibers into the composite core memberoffers substantial improvements in strength to weight ratio overmaterials commonly used for cable in an electrical power transmissionsystem. Fibers may be selected from the group comprising, for example:carbon fibers—both HM and HS (pitch based), Kevlar fibers, basaltfibers, glass fibers, Aramid fibers, boron fibers, liquid crystalfibers, high performance polyethylene fibers and carbon nanofibers.Several types of carbon, boron, Kevlar and glass fibers are commerciallyavailable. Each fiber type has subtypes of varying characteristics thatmay be combined in various combinations in order to achieve a particularcomposite. It is noted that these are only examples of fibers that meetthe specified characteristics of the invention, such that the inventionis not limited to these fibers only. Other fibers meeting the requiredphysical characteristics of the invention may be used.

Composite cores of the present invention preferably comprise fiber towshaving relatively small yield or K numbers. A fiber tow is an untwistedbundle of continuous microfibers wherein the composition of the tow isindicated by its yield or K number. For example, 12K tow has 12,000individual microfibers. Ideally, microfibers wet out with resin suchthat the resin coats the circumference of each microfiber within thebundle or tow. Wetting may be affected by tow size, that is, the numberof microfibers in the bundle, and individual microfiber size. Largertows create more difficulty wetting around individual fibers in thebundle due to the number of fibers contained within the bundle whereassmaller fiber diameter increases the distribution of resin around eachfiber within each fiber tow. Wetting and infiltration of the fiber towsin composite materials is of critical importance to performance of theresulting composite. Incomplete wetting results in flaws or dry spotswithin the fiber composite reducing strength and durability of thecomposite product. Fiber tows may also be selected in accordance withthe size of fiber tow that the process can handle in order to enableforming a composite having optimal desired physical characteristics. Oneprocess for forming composite cores in accordance with the presentinvention is called B-stage forming process. Fiber tows of the presentinvention for carbon are selected preferably in the range of about 4K toabout 50K and glass fiber tows are preferably selected in the range ofabout 800 to about 1200 yield.

Individual reinforced fiber sizes in accordance with the presentinvention preferably are within the range of about 8 to about 15 μm forglass fibers and most preferably about 10 μm in diameter whereas carbonfibers are preferably in the range of about 5 to about 10 μm and mostpreferably about 7 μm in diameter. For other types of fibers a suitablesize range is determined in accordance with the desired physicalproperties. The ranges are selected based on optimal wet-outcharacteristics and feasibility. For example, fibers less than about 5μm are so small in diameter that they pose certain health risks to thosethat handle the fibers. On the other end, fibers approaching 25 μm indiameter are difficult to work with because they are stiffer and morebrittle.

Composite cores of the present invention comprise fiber tows that aresubstantially continuous in length. In practice, carbon fiber towscomprising the present invention are preferably between about 1000 and3000 meters in length, depending on the size of the spool. However,glass fiber lengths can range up to 36 km depending on the size of thespool. Most preferably, fibers are selected in the range of 1000 to33,000 meters. It is most preferable to select the longest fibers thatthe processing equipment will accommodate due to less splicing of fibersto form a continuous composite core in excess of 6000 feet. Fiber endsmay be glued end-to-end forming a substantially continuous fiber towlength. Continuous towing orients the fibers longitudinally along thecable.

Composite cores of the present invention comprise fibers having a highpacking efficiency relative to other conductor cable cores. Inparticular, traditional steel conductor cables generally compriseseveral round steel wires. Due to the round shape of the wires, thewires cannot pack tightly together and can only achieve a packingefficiency of about 74%. The only way that a steel core could have 100%packing efficiency would be to have a solid steel rod as opposed toseveral round steel wires. This is not possible because the final cablewould be to stiff and would not bend. In the present invention,individual fibers are oriented longitudinally, wherein each fiber iscoated with resin. and cured forming a hybridized composite core memberhaving 100% packing efficiency. Higher packing efficiency yields acomposite strength that is greater for a given volume relative to othercables. In addition, higher packing efficiency allows for formation of acomposite core of smaller diameter thereby increasing the amount ofaluminum conductor material capable of wrapping around the compositeconductor core.

Composite cores of the present invention comprise reinforced fibers thatare substantially heat resistant. Heat resistance enables an ACCC cableto transmit increased power due to the ability of the composite core towithstand higher operating temperatures. The fibers used in the presentinvention have the ability to withstand operating temperatures betweenthe range of about 90 and about 230° C. Most preferably, the fibers inthe present invention have the ability to withstand operatingtemperatures between the range of about 170 to 200° C. Moreover, fibersused in the present invention can preferably withstand an ambienttemperature range between about −40 to about 90° C. That is, underambient conditions with no current flowing in an ACCC cable, thecomposite core is able to withstand temperatures as low as about −40° C.without suffering impairment of physical characteristics.

Relative amounts of each type of reinforced fiber varies depending onthe desired physical characteristics of the composite cable. Forexample, fibers having a lower modulus of elasticity enable formation ofa high strength, stiff composite core. Carbon fibers have a modulus ofelasticity preferably in the range of about 22 to about 37 Msi whereasglassfibers are considered low modulus reinforced fibers The two typesof fibers may be combined to take advantage of the inherent physicalproperties of each fiber to create a high strength, high stiffnesscomposite core with added flexibility. In one embodiment, for example,the composite core comprises an inner carbon/resin core having an areaof 0.037 sq. in. and a fiber resin ratio of about 70/30 by weight and anouter glass/epoxy layer having an area of 0.074 sq. in. and afiber/resin ratio of about 75/25 by weight.

In accordance with the present invention, the physical characteristicsof the composite core may be adjusted by adjusting the fiber/resin ratioof each component. Alternatively, the physical characteristics of thecomposite core may be adjusted by adjusting the area percentage of eachcomponent within the composite core member. For example, by reducing thetotal area of carbon from 0.037 sq. in. and increasing the area of glassfrom 0.074 sq. in., the composite core member product has reducedstiffness in the carbon core coupled with increased flexibility. Inaddition, due to the smaller tow diameter of glass compared to carbon,the resulting composite core is smaller in diameter enabling increasedconductor for the same resulting cable size. Alternatively, a thirdfiber, for example basalt, may be introduced into the composite core.The additional fiber changes the physical characteristics of the endproduct. For example, by substituting basalt for some carbon fibers, thecore has increased dielectric properties and a relative decrease in corestiffness.

Composite cores of the present invention comprise reinforced fibershaving relatively high tensile strength. The degree of sag in anoverhead voltage power transmission cable varies as the square of thespan length and inversely with the tensile strength of the cable suchthat an increase in the tensile strength effectively reduces sag in anACCC cable. Carbon fibers are selected having a tensile strengthpreferably in the range of about 350 to about 750 Ksi. More preferablyin the range between 710 Ksi to 750 Ksi. Glassfibers are selected havinga tensile strength preferably in the range of about 180 to about 220Ksi. The tensile strength of the composite is enhanced by combiningglassfibers having a lower tensile strength with carbon fibers having ahigher tensile strength. The properties of both types of fibers arecombined to form a new cable having a more desirable set of physicalcharacteristics.

Composite cores of the present invention comprise longitudinal fibersembedded within a resin matrix having a fiber/resin volume fraction in aratio of at least 50:50%. The volume fraction is the area of fiberdivided by the total area of the cross section wherein the weight of thefiber will determine the final percentage ratio by weight. In accordancewith the invention, preferably the volume fraction of fiber in thefiber/resin composite is within the range of about 50 to about 57% byvalue. Most preferably, the volume fraction is calculated to yield afiber/resin ratio of 72% by weight depending on the weight of the fiber.

In accordance with the present invention, the composite core is designedbased on the desired physical characteristics of an ACCC reinforcedcable. More preferably, the composite core is designed having an innerstrengthening core member comprising an advanced composite surrounded byan outer more flexible layer. An advanced composite is a compositehaving continuous fibers having a greater than 50% volume fraction andmechanical properties exceeding the mechanical properties ofglassfibers. Further, it is preferable to have an outer layer lowmodulus composite having mechanical properties in the range of glassfiber. A low modulus fiber has mechanical characteristics in the rangeof glass fiber. The mechanical properties of glass fibers accommodatesplicing whereas the advanced composite is more brittle and does notundertake splicing well.

Fibers forming an advanced composite are selected preferably having atensile strength in the range of about 350 to about 750 Ksi; a modulusof elasticity preferably in the range of about 22 to about 37 Msi; acoefficient of thermal expansion in the range of about −0.7 to about 0m/m/C; yield elongation percent in the range of about 1.5 to 3%;dielectric properties in the range of about 0.31 W/m·K to about 0.04W/m·K and density in the range of about 0.065 lb/in³ to about 0.13lb/in³.

Fibers forming the outer low modulus layer surrounding the advancedcomposite preferably have a tensile strength in the range within about180 to 220 Ksi; a coefficient of thermal expansion in the range of about5×10⁻⁶ to about 10×10⁻⁶ m/m/C; yield elongation percent in the range ofabout 3 to about 6%; and dielectric properties in the range of about0.034 to about 0.04 W/m·K and density in the range of about 0.065 toabout 0.13 lbs/in³.

A composite core member having an inner core comprising an advancedcomposite in accordance with the preferred ranges of values set forthabove surrounded by an outer low modulus layer in accordance with thepreferred ranges of values set forth above, has increased ampacity overother conductor cables by about 0 to about 200%. In particular, thefinal composite core has the following preferable physicalcharacteristics. Tensile strength in the range within about 160 to about240 Ksi. More preferably, having tensile strength of about 185 Ksi.Modulus of elasticity preferably in the range of within about 7 to about30 Msi. More preferably, having a modulus of elasticity of about 14 Msi.Operating temperature in the range within about 90 to about 230° C. Morepreferably, the composite core is able to withstand operatingtemperatures at least about 190° C. Thermal expansion coefficient withinthe range of about 0 to about 6×10⁻⁶ m/m/C. More preferably, the corethermal expansion coefficient is about 2.5×10⁻⁶ m/m/C.

Preferably, particular combinations of reinforced fibers are selectedbased on the reinforced fiber's inherent physical properties in order toproduce a composite core product having particular physical properties.In particular, to design an ACCC cable able to withstand ampacity gains,the composite core comprises both a higher modulus of elasticity and alower coefficient of thermal expansion. The fibers preferably are notconductive but have high dielectric properties. An ACCC cable operatesat higher operating temperatures without a corresponding increase insag. Sag versus temperature calculations require input of modulus ofelasticity, thermal expansion coefficient, weight of the compositestrength member and conductor weight. Accordingly, these physicalcharacteristics are taken into account in designing the composite core.

While it is preferable to form a composite core having an inner advancedcomposite surrounded by a low modulus composite, it is feasible to makea composite core comprising interspersed high modulus of elasticityfibers and low modulus of elasticity fibers. Depending on thestrain:failure ratio, this type of core may have to be segmented inorder to achieve an appropriate degree of winding. Moreover, thecomposite core is designed having the fiber of increased modulus ofelasticity in the inner core surrounded by a fiber having a lowermodulusof elasticity due to the decreased degree of strain on the innercore.

For example, carbon is selected for high modulus of elasticity in therange of about 22 to about 37 Msi, low thermal expansion coefficient inthe range of about −0.7 to about 0 m/m/C, and elongation percent in therange of about 1.5 to about 3%. Glassfibers are selected for low modulusof elasticity, low thermal expansion coefficient in the range of about5×10⁻⁶ to about 10×10⁻⁶ m/m/C and elongation percent in the range ofabout 3 to about 6%. The strain capability of the composite is tied inwith the inherent physical properties of the components and the volumefraction of components. After the fiber/resin composite is selected,the-strain to failure ratio of each fiber/resin composite is determined.In accordance with the present invention, the resins can be customizedto achieve certain properties for processing and to achieve desiredphysical properties in the end product. As such, the fiber/customizedresin strain to failure ratio is determined. For example, carbon/epoxyhas a strain to failure ratio of 2.1% whereas glassfiber/epoxy has astrain to failure ratio of 1.7%. Accordingly, the composite core isdesigned having the stiffness of the carbon/epoxy in the inner core andthe more flexible glassfiber/epoxy in the outer core to create acomposite core with the requisite flexibility and low thermal expansioncoefficient.

Alternatively, another advanced composite having mechanical propertiesin excess of glassfiber could be substituted for at least a portion ofthe carbon fibers and another fiber having the mechanical property rangeof glassfiber could be substituted for glassfiber. For example, basalthas the following properties: high tensile strength in the range ofabout 701.98 Ksi (compared to the range of about 180 to about 500 Ksifor glassfibers), high modulus of elasticity in the range of about 12.95Msi, low thermal expansion coefficient in the range of about 8.0 ppm/C(compared to about 5.4 ppm/C for glassfibers), and elongation percent inthe range of about 3.15% (compared the range of about 3 to about 6% forglassfibers). The basalt fibers provide increased tensile strength, amodulus of elasticity between carbon and glassfiber and an elongation %close to that of carbon fibers. A further advantage is that basalt hassuperior dielectric properties to carbon. Preferably, the composite corecomprises an inner strength member that is non-conductive. By designingan advanced composite core having fibers of inherent physicalcharacteristics surrounded by low modulus fiber outer core, a newproperty set for the composite core is obtained.

Sag versus temperature is determined by considering the modulus ofelasticity, the thermal expansion coefficient, the weight of thecomposite strength member, and the conductor weight. The higher modulusof elasticity and lower coefficient of thermal expansion in theresulting composite core enables an ACCC cable to withstand ampacitygains and operating temperatures between about 90 to about 230° C.

The composite core of the present invention comprises thermosettingresins having physical properties that are adjustable to achieve theobjects of the present invention. Depending on the intended cableapplication, suitable thermosetting resins are selected as a function ofthe desired cable properties to enable the composite core to have longterm durability at high temperature operation. Suitable thermosettingresins may also be selected according to the process for formation ofthe composite core in order to minimize friction during processing,increase process speed and preferable viscosity to achieve theappropriate fiber/resin ratio in the final composite core.

The composite core of the present invention comprises resins having goodmechanical properties and chemical resistance at prolonged exposure forat least about 60 years of usage. More preferably, the composite core ofthe present invention comprises resins having good mechanical propertiesand chemical resistance at prolonged exposure for at least about 70years of usage. Further, the composite core of the present inventioncomprises resins that operate preferably within the range of about 90 toabout 230° C. More preferably, the resin operates within the range ofabout 170 to about 200° C.

The composite core of the present invention comprises a resin that istough enough to withstand splicing operations without allowing thecomposite body to crack. An essential element of the present inventionis the ability to splice the composite core member in the final cableproduct. The composite core of the present invention comprises resinhaving a neat resin fracture toughness preferably within the range ofabout 0.87 INS-lb/in to about 1.24 INS-lb/in.

The composite core of the present invention comprises a resin having alow coefficient of thermal expansion. A low coefficient of thermalexpansion reduces the amount of sag in the resulting cable. A resin ofthe present invention preferably operates in the range of about 15×10⁻⁶C and about 42×10⁻⁶ C. The composite core of the present inventioncomprises a resin having an elongation greater than about 4.5%.

A composite core of the present invention comprises fibers embedded in ahigh temperature resin having at least a 50% volume fraction. The fiberto resin ratio affects the physical properties of the composite coremember. In particular, the strength, electrical conductivity, andcoefficient of thermal expansion are functions of the fiber volume ofthe composite core. Generally, the higher the volume fractions of fibersin the composite, the higher the tensile strength for the resultingcomposite. A fiber to resin volume fraction of the present inventionpreferably is within the range of about 50 to 57% corresponding topreferably within about 62 to about 75% by weight. More preferably, thefiber/resin ratio in the present invention is about 65 to about 72% byweight. Most preferably, the fiber volume fraction in the presentinvention meets or exceeds about 72% by weight.

Each fiber type of the composite core may have a different fiber/resinratio by weight relative to the other fibers. This is accomplished byselecting the appropriate number of each fiber type and the appropriateresin type to achieve the desired ratio. For example, a composite coremember having a carbon/epoxy inner core surrounded by an outerglass/epoxy layer may comprise 126 spools of glass fiber and epoxy resinhaving a viscosity of about 2000 to about 6000 cPs at 50° C. whichyields a pre-determined fiber/resin ratio of about 75/25 by weight.Preferably, the resin may be tuned to achieve the desired viscosity forthe process. The composite may also have 16 spools of carbon fiber andepoxy resin having a viscosity of about 2000 to about 6000 cPs at 50° C.which yields a predetermined fiber/resin ratio of about 70/30 by weight.Changing the number of spools of fiber changes the fiber/resin by weightratio thereby changing the physical characteristics of the compositecore product. Alternatively, the resin may be adjusted therebyincreasing or decreasing the resin viscosity to change the fiber/resinratio.

The composite cables made in accordance with the present inventionexhibit physical properties wherein these certain physical propertiesmay be controlled by changing parameters during the composite coreforming process. More specifically, the composite core forming processis adjustable to achieve desired physical characteristics in a finalACCC cable.

In accordance with the invention, a multi-phase B-stage forming processproduces a composite core member from substantially continuous lengthsof suitable fiber tows and heat processable resins. In a further step,the composite core member is wrapped with high conductivity aluminum.

A process for making composite cores for ACCC cables according to theinvention is described as follows. Referring to FIG. 1, the conductorcore B-stage forming process of the present invention is shown anddesignated generally by reference number 10. The B-stage forming process10 is employed to make continuous lengths of composite core members fromsuitable fiber tows or rovings and heat processable resins. Theresulting composite core member comprises a hybridized concentric corehaving an inner and outer layer of uniformly distributed substantiallyparallel fibers.

In starting the operation, the pulling and winding spool mechanism isactivated to commence pulling. The unimpregnated initial fiber towsextending from the exit end of the cooling portion in zone 9 serve asleaders at the beginning of the operation to pull fiber tows 12 fromspools 11 through fiber tow guide 18 and the composite core processingsystem.

In FIG. 1, multiple spools of fiber tows 12 are contained within a racksystem 14 and are provided with the ends of the individual fiber tows12, leading from spools 11, being threaded through a fiber tow guide 18.The fibers undergo tangential pulling to prevent twisted fibers.Preferably, a pulling device 34 at the end of the apparatus pulls thefibers through the apparatus. Each dispensing rack 14 comprises a deviceallowing for the adjustment of tension for each spool 11. For example,each rack 14 may have a small brake at the dispensing rack toindividually adjust the tension for each spool. Tension adjustmentminimizes catemary and cross-over of the fiber when it travels and aidsin the wetting process. The tows 12 are pulled through the guidelS andinto a preheating oven 20 that evacuates moisture. The preheating oven20 uses continuous circular air flow and a heating element to keep thetemperature constant.

The tows 12 are pulled into a wet out tank 22. Wet out tank 22 is filledwith resin to impregnate the fiber tows 12. Excess resin is removed fromthe fiber tows 12 during wet out tank 22 exit. The fiber tows 12 arepulled from the wet out tank 22 to a secondary system, B-stage oven 24.The B-stage oven heats the resin to a temperature changing the liquidstage of resin to a semi-cure stage. B-stage cure resin is in a tackystage which permits the fiber tows 12 to be bent, changed, compressedand configured. The tackiness is controlled by manipulation of the typeof resin, the fiber type, thread count and size of the fibers andtemperature of the oven. Fiber tows 12 maintained separated by the guide18, are pulled into a second B-stage oven 26 comprising a plurality ofconsecutive bushings to compress and configure the tows 12. In thesecond B-stage oven 26, the fiber tows 12 are directed through aplurality of passageways provided by the bushings. The consecutivepassageways continually compress and configure the fiber tows 12 intothe final uniform composite core member.

Preferably, the composite core member is pulled from the second B-stageoven 26 to a next oven processing system 28 wherein the composite coremember is cured and pulled to a next cooling system 30 for cooling.After cooling, the composite core is pulled to a next oven processingsystem 32 for post curing at elevated temperature. The post-curingprocess promotes increased cross-linking within the resin matrixresulting in improved physical characteristics of the composite member.The process generally allows an interval between the heating and coolingprocess and the pulling apparatus 36 to cool the product naturally or byconvection such that the pulling device 34 used to grip and pull theproduct will not damage the product. The pulling mechanism pulls theproduct through the process with precision controlled speed.

Referring now more particularly to FIG. 1, in a preferred embodiment,the process continuously pulls fiber from left to right of the systemthrough a series of phases referred to herein as zones. Each zoneperforms a different processing function. In this particular embodiment,the process comprises 9 zones. The process originates from a series offiber dispensing racks 14 whereby a caterpuller 34 continuously pullsthe fibers 12 through each zone. One advantage to the caterpullar systemis that it functions as a continuous pulling system driven by anelectrical motor as opposed to the traditional reciprocation system. Thecaterpullar system uses a system of two belts traveling on the upper andlower portions of the product squeezing the product there between.Accordingly, the caterpuller system embodies a simplified uniformpulling system functioning at precision controlled speed using only onedevice instead of a multiplicity of interacting parts functioning topropel the product through the process. Alternatively, a reciprocationsystem may be used to pull the fibers through the process.

The process starts with zone 1. Zone 1 comprises a type of fiberdispensing system. Fibers that can be used for example are: glassfibers, carbon fibers, both HM and HS (pitch based), basalt fibers,Aramid fibers, liquid crystal fibers, Kevlar fibers, boron fibers, highperformance polyethylene fibers and carbon nanofiber (CNF). In oneembodiment, the fiber dispensing system comprises two racks 13 each rackcontaining a plurality of spools 11 containing fiber tows 12. Further,the spools 11 are interchangeable to accommodate varying types of fibertows 12 depending on the desired properties of the composite coremember.

For example, a preferred composite core member formed by the B-stageforming process comprises a carbon/resin inner core surrounded by aglass/resin outer core layer. Preferably, high strength and high qualitycarbon is used. The resin matrix also protects the fibers from surfacedamage, and prevents cracking through a mass of fibers improvingfracture resistance. The conductor core B-stage forming process 10creates a system for pulling the fibers to achieve the optimum degree ofbonding between fibers in order to create a composite member withoptimal composite properties.

As previously mentioned, the components of the composite core areselected based on desired composite core characteristics. One advantageof the process is the ability to adjust composite components in orderfor a composite core to achieve the desired goals of a final ACCC cable,namely, a cable that can carry current without undue thermal expansioncausing sag and without tensile strength reduction. It is preferable tocombine types of fibers to combine the physical characteristics of each.Performance can be improved by forming a core with increased strengthand stiffness, coupled with a more flexible outer layer. The processincreases the optimal characteristics of the composite by preventingtwisting of rovings leading to more uniform wetting and strengthcharacteristics.

For example, in a preferred embodiment of the composite core member, thecomposite core comprises glass and carbon. Using the B-stage formingprocess, the racks 13 hold 126 spools 11 of glass and 16 spools 11 ofcarbon. The fiber tows 12 leading from spools 11 are threaded through afiber tow guide 18 wherein fiber tow passageways are arranged to providea configuration for formation of a core composite member having auniform carbon core and outer glass layer. The carbon layer ischaracterized by high strength and stiffness and is a weak electricalconductor whereas the outer low modulus glass layer is more flexible andnon-conductive. Having an outer glass layer provides an outer insulatinglayer between the carbon and the high conductivity aluminum wrapping inthe final composite conductor product.

The fiber dispensing system dispenses fiber tangent from the fiberpackage pull. Tangent pull from the spool will not twist the fiber. Thecenter pull method will twist fibers dispensed from the spool. As such,the center pull method results in an increased number of twisted fibers.Twisted fiber will occasionally lay on top of other twisted fiber andcreate a composite with multiple spots of dry fiber. It is preferable touse tangent pull to avoid dry spots and optimize wet out ability of thefibers.

The fiber tows 12 are threaded through a guidance system 18. Preferably,the guide 18 comprises a polyethylene and steel bushings containing aplurality of passageways in a predetermined pattern guiding the fibersto prevent the fibers from crossing. Referring to FIG. 2, the guidecomprises a bushing with sufficiently spaced passageways for insertionof the fibers in a predetermined pattern. The passageways are containedwithin an inner square portion 40. The passageways are arranged in rowsof varying number wherein the larger diameter carbon fibers pass throughthe center two rows of passageways 42 and the smaller diameter glassfibers pass through the outer two rows 44 on either side of the carbonpassageways 42. A tensioning device, preferably on each spool, adjuststhe tension of the pulled fibers and assures the fibers are pulledstraight through the guide 18.

At least two fibers are pulled through each passageway in the guide 18.For example, a guide 18 comprising 26 passageways pulls 52 fibersthrough, wherein each passageway has two fibers. If a fiber of a pairbreaks, a sensing system alerts the composite core B-stage formingprocess 10 that there is a broken fiber and stops the puller 34.Alternatively, in one embodiment, a broken fiber alerts the process andthe repair can be made on the fly without stopping the process dependingon where the breakage occurs. To repair, a new fiber is pulled from therack 13 and glued to the broken end of the new fiber. After the fiber isrepaired, the conductor core B-stage forming machine 10 is startedagain.

In preferred form, the fibers are grouped in a parallel arrangement fora plurality of rows. For example, in FIG. 2, there are six parallel rowsof passageways. The outer two rows comprise 32 passageways, the twoinner rows comprise 31 passageways, and the two center rows comprise 4passageways each. Fibers are pulled at least two at a time into eachpassageway and pulled into zone 2.

Zone 2 comprises an oven processing system that preheats the dry fibersto evacuate any moisture. The fibers of the present invention arepreferably heated within the range of about 150 to 250° F. to evaporatemoisture.

The oven processing system comprises an oven portion wherein the ovenportion is designed to promote cross-circular air flow against the flowof material. FIG. 9 illustrates a typical embodiment of the oven system.An oven is generally designated 60. The fibers pass through the ovenfrom upstream to downstream direction, the air passes in the reversedirection. The oven processing system comprises a heat drive systemhousing 64 that houses a blower 68 powered by electric motor 70 locatedupstream from a heater assembly 66 to circulate air in a downstreamdirection through air flow duct 62. The heat drive system housing housesa blower 68 upstream of the heater assembly 66. The blower 68 propelsair across the heater assembly 66 and through the oven system. The airflows downstream to a curved elbow duct 72. The curved elbow duct 72shifts air flow 90 degrees up into an inlet duct 78 and through the oveninlet 76. Through the inlet air flow shifts 90 degrees to flow upstreamthrough the oven 60 against the pull direction of the fibers. At the endof the oven 60, the air flow shifts 90 degrees down through the ovenoutlet 80 through the outlet duct 74 through the motor 70 and back intothe heat drive system housing 64. The motor 70 comprises an electricalmotor outside of the heat drive system to prevent overheating. The motor70 comprises a pulley with a timing belt that moves the bladed blower68. Preferably, the system is computer controlled allowing continuousair circulation at a desired temperature. More preferably, the processallows for the temperature to change at any time according to the needsof the process.

For example, the computer senses a temperature below the requiredtemperature and activates the heating element or disactivate the heaterwhen the temperature is too high. The blower blows air across theheating element downstream. The system forces the air to travel in aclosed loop circle continuously circulating through the oven keeping thetemperature constant.

FIG. 10 is a more detailed view of a preferred embodiment of the heatingelement 66. In one embodiment, the heater assembly comprises ninehorizontal steel electrical heaters 82. Each heater unit is separate anddistinct from the other heater.

Each heater unit is separated by a gap. Preferably, after sensing atemperature differential, the computer activates the number of heatersto provide sufficient heat. If the system requires the computeractivates one of nine heaters. Alternatively, depending on the needs ofthe process, the computer activates every other heater in the heaterassembly. In another embodiment the computer activates all heaters inthe heater assembly. In a further alternative, the computer activates aportion of the heaters in the heater assembly or turns all the heatersoff.

In an alternate embodiment, electromagnetic fields penetrate through theprocess material to heat the fibers and drive off any moisture. Inanother embodiment pulsed microwaves heat the fibers and drive off anymoisture. In another embodiment, electron beam processing uses electronsas ionizing radiation to drive off any excess moisture.

In another embodiment, the puller pulls the fibers from zone 2 to zone3, the fiber impregnation system. Zone 3 comprises a wet out tank 22. Ina preferred embodiment, the wet out tank 22 contains a device thatallows the redirection of fibers during wet out. Preferably, the deviceis located in the center of the tank and moves the fibers vertically upand down perpendicular to the direction of the pull whereby thedeflection causes the fibers to reconfigure from a round configurationto a flat configuration. The flat configuration allows the fibers to layside by side and allows for the fibers to be more thoroughly wetted bythe resin.

Various alternative techniques well known in the art can be employed toapply or impregnate the fibers with resin. Such techniques include forexample, spraying, dipping, reverse coating, brushing and resininjection. In an alternate embodiment, ultrasonic activation usesvibrations to improve the wetting ability of the fibers.

Generally, any of the various known heat curable thermosetting polymericresin compositions can be used with the invention. The resin may be forexample, PEAR (PolyEther Amide Resin), Bismaleimide, Polyimide,liquid-crystal polymer (LCP), and high temperature epoxy based on liquidcrystal technology or similar resin materials. Resins are selected basedon the process and the physical characteristics desired in the compositecore.

Further, the viscosity of the resin affects the rate of formation. Toachieve the desired proportion of fiber/resin for formation of thecomposite core member, preferably the viscosity ranges within the rangeof about 200 to about 1500 Centipoise at 20° C. More preferably, theviscosity falls in the range of about 200 to about 600 Centipoise 20° C.The resin is selected to have good mechanical properties and excellentchemical resistance to prolonged exposure of at least 60 years and morepreferably, at least 70 years of operation up to about 230° C. Aparticular advantage of the present invention is the ability for theprocess to accommodate use of low viscosity resins. In accordance withthe present invention, it is preferable to achieve a fiber/resin ratiowithin the range of 62-75% by weight. More preferable is a fiber/resinratio within the range of 72-75% by weight. Low viscosity resins willsufficiently wet the fibers for the composite core member. A preferredpolymer provides resistance to a broad spectrum of aggressive chemicalsand has very stable dielectric and insulating properties. It is furtherpreferable that the polymer meets ASTME595 outgassing requirements andUL94 flammability tests and is capable of operating intermittently attemperatures ranging between 220 and 280° C. without thermally ormechanically damaging the strength member.

To achieve the desired fiber to resin ratio, the upstream side of thewet out tank comprises a number of redirectional wiping bars. As thefibers are pulled through the wet out tank the fibers are adjusted upand down against a series of wiping bars removing excess resin.Alternatively, the redirection system comprises a wiper system to wipeexcess resin carried out of the tank by the fibers. Preferably, theexcess resin is collected and recycled into the wet out tank 22.

Alternatively, the wet out tank uses a series of squeeze out bushings toremove excess resin. During the wet out process each bundle of fibercontains as much as three times the desired resin for the final product.To achieve the right proportion of fiber and resin in the cross sectionof the composite core members, the amount of pure fiber is calculated.The squeeze out bushing in designed to remove a predetermined percentageof resin. For example, where the bushing passageway is twice as big asthe area of the cross section of the fiber, a resin concentrationgreater than 50% by value won't be pulled through the bushing, theexcess resin will be removed. Alternatively, the bushing can be designedto allow passage of 100% fiber and 20% resin.

Preferably, a recycle tray extends lengthwise under the wet out tank 22to catch overflow resin. More preferably, the wet out tank has anauxiliary tank with overflow capability. Overflow resin is returned tothe auxiliary tank by gravity through the piping. Alternatively, tankoverflow is captured by an overflow channel and returned to the tank bygravity. In a further alternate, the process uses a drain pump system torecycle the resin back through the auxiliary tank and into the wet outtank. Preferably, a computer system controls the level of resin withinthe tank. Sensors detect low resin levels and activate a pump to pumpresin into the tank from the auxiliary mixing tank into the processingtank. More preferably, there is a mixing tank located within the area ofthe wet out tank. The resin is mixed in the mixing tank and pumped intothe resin wet out tank.

The pullers pull the fibers from zone 3 to zone 4, the B-stage zone.Zone 4 comprises an oven processing system 24. Preferably, the ovenprocessing system is an oven with a computer system that controls thetemperature of the air and keeps the air flow constant wherein the ovenis the same as the oven in zone 2.

The pullers pull the fibers from zone 3 to zone 4. The oven circulatesair in a circular direction downstream to upstream by a propellerheating system. The computer system controls the temperature at atemperature to heat the wet fiber to B-stage. Preferably, the processdetermines the temperature. B-stage temperature of the present inventionranges from within about 200 to 250° F. One advantage of the B-stagesemi-cure process in the present invention is the ability to heat theresin to a semi-cure state in a short duration of time, approximately1-1.5 minutes during the continuation of the process. The advantage isthat the heating step does not affect the processing speed of thesystem. The B-stage process allows for the further tuning of thefiber/resin ratio by removing excess resin from the wet-out stage.Further, B-stage allows the fiber/resin matrix to be further compactedand configured during the process. Accordingly, the process differs fromprevious processes that use pre-preg semi-cure. Heating semi-cures thefibers to a tacky stage.

More specifically, in traditional composite processing applications, thewetted fibers are heated gradually to a semi-cure stage. However, theheating process generally takes periods of one hour or longer to reachthe semi-cure stage. Moreover, the composite must be immediately wrappedand frozen to keep the composite at the semi-cure stage and preventcuring to a final stage. Accordingly, the processing is fragmentedbecause it is necessary to remove the product from the line to configurethe product.

In accordance with the present invention, the B-stage heating isdedicated to a high efficiency commercial application wherein semi-cureis rapid, preferably 1-1.5 minutes during a continuous process in linewithin the process. Preferably, the resins are designed to allow rapidB-stage semi-curing that is held constant through the process allowingfor shaping and configuring and further compaction of the product.

The pullers pull the fibers from B-stage zone 4 to zone 5 for theformation of the composite core member. Zone 5 comprises a next ovenprocessing system 26 having a plurality of bushings. The bushingsfunction to shape the cross section of the fiber tows 12. Preferably,the bushings are configured in a series comprising a parallelconfiguration with each other. In this embodiment, there is a set ofseven bushings spaced laterally within the oven processing system 26.Preferably, the spacing of the bushings are adjusted according to theprocess. The bushings can be spaced equi-distance or variable distancefrom each other.

The series of bushings in zone 5 minimize friction due to the relativelythin bushing ranging within about ½ to ⅜ inch thick. Minimizing frictionaids in maximizing the process speed.

Zones 4, 5 and 6 of the present invention extends within the range ofabout 30-45 feet. Most preferably, the zones 4, 5 and 6 extend at least30 feet. This pulling distance and the decreased friction due to thinbushing plates aids in achieving a desired pull speed in the range ofabout 9 ft/min to about 50 ft/min. Most preferably about 20 ft/min.Processing speed is further increased due to the high fiber/resin ratio.

Referring to FIG. 3, for example, the bushings 90 comprise a flat steelplate with a plurality of passageways through which the fiber tows 12are pulled. The flat plate steel bushing 90 preferably ranges from ⅜inch to ½ inch thick determined by the process. The bushings 90 haverelatively thin walls to reduce friction and the amount of heat whichmust be added or removed by the heating and cooling process in order toachieve the temperature changes required to effect curing of the fiberresin matrix. The thickness of the bushing 90 is preferably the minimumthickness required to provide the structural strength necessary toconstrain forces imposed upon the bushing 90 by the material passingtherethrough. In particular, the thickness of the bushing 90 ispreferably the minimum needed to limit deformation of the bushing wallto a tolerable level which will not interfere with the pulling of thematerial through the system.

Preferably, the design and size of the bushings 90 are the same. Morepreferably, the passageways within each bushing 90 diminish in size andvary in location within each successive bushing 90 in the upstreamdirection. FIG. 3 illustrates a preferred embodiment of a bushing 90.The bushing 90 comprises two hooked portions 94 and an inner preferablysquare portion 92. The inner square portion 92 houses the passagewaysthrough which the pulling mechanism pulls the fibers. The outer hookedportions 94 form a support system whereby the bushing 90 is placedwithin the oven in zone 5. The outer hooked portion 94 connects withinterlocking long steel beams within the oven that function to supportthe bushings 90.

Zone 5 comprises a series of eight consecutive bushings. The bushingshave two functions: (1) guide the fiber in the configuration for thefinal product; and (2) shape and compress the fibers. In one embodiment,the bushings 90 are placed apart within the oven supported on the hookedstructures. The bushings 90 function to continually compress the fibersand form a composite core comprising, in this embodiment, carbon andglass while the process is under appropriate tension to achieveconcentricity and uniform distribution of fiber without commingling offibers. The bushings 90 may be designed to form bundles of a pluralityof geometries. For example, FIG. 5 illustrates the variations in crosssections in composite member. Each cross section results from differentbushing 90 design.

The passageways in each successive bushing 90 diminish in size furthercompacting the fiber bundles. For example, FIG. 6 shows each bushing 90superimposed on top of one another. Several changes are apparent witheach consecutive bushing 90. First, each overlayed bushing 90 shows thatthe size of each passageway decreases. Second, the superimposed figureshows the appearance of the center hole for compaction of the coreelement. Third, the figure shows the movement of the outer cornerpassageways towards the center position.

Referring to FIG. 4, there are two bushings illustrated. The firstbushing 100 illustrated, is in a similar configuration as the guidebushing 18. The second bushing 104 is the first in the series ofbushings that function to compress and configure the composite core. Thefirst bushing 100 comprises an inner square portion 92 with a pluralityof passageways 102 prearranged through which the fibers are pulled. Thepassageways 102 are designed to align the fibers into groups in bushingtwo 104 having four outer groups 106 of fibers and four inner groups 108of fibers. The inner square portion of the bushing 100 comprises sixrows of passageways 110. The arrangement of the passageways 110 may beconfigured into any plurality of configurations depending on the desiredcross section geometry of the composite core member. The top and bottomrow, 112 and 114 respectively, contain the same number of passageways.The next to top and next to bottom rows, 116 and 118 respectively,contain the same number of passageways and the two inner rows 120 and122 contain the same number of passageways.

In a preferred embodiment, the top and bottom rows contain 32passageways each. The next level of rows contain 31 passageways each.The middle rows contain 4 passageways each. The pulling mechanism pullstwo fibers through each passageway. Referring to FIG. 4 for example, thepulling mechanism pulls 126 glass fibers through rows 112, 114, 116 and118. Further, the pulling mechanism pulls 16 carbon fibers through rows120 and 122.

Referring to FIG. 7, the next bushing 130, bushing three in the seriescomprises an inner square portion 131 having four outer cornerpassageways 132 a, 132 b, 132 c and 132 d and four inner passageways 134a, 134 b, 134 c and 134 d. The fibers exit bushing two and are dividedinto equal parts and pulled through bushing three. Each passageway inbushing three comprises one quarter of the particular type of fiberpulled through bushing two. More specifically, the top two rows of thetop and the bottom of bushing two are divided in half whereby the righthalf of the top two rows of fibers are pulled through the right outercorner of bushing three. The left half of the top two rows of fibers arepulled through the upper left corner 132 a of bushing three 130. Theright half of the top two rows of fibers are pulled through the upperright corner 132 b of bushing three 130. The right half of the bottomtwo rows of fibers are pulled through the lower right corner 132 c ofbushing three. The left half of the bottom two rows of fibers are pulledthrough the lower left corner 132 d of bushing three 130. The inner tworows of bushing one are divided in half whereby the top right half ofthe top middle row of fibers is pulled through the inner upper rightcorner 134 b of bushing three 130. The left half of the top middle rowof fibers is pulled through the inner upper left corner 134 a of bushingthree 130. The right half of the lower middle row of fibers is pulledthrough the inner lower right corner 134 c of bushing three 130. Theleft half of the lower middle row of fibers is pulled through the innerlower left corner 134 d of bushing three 130. Accordingly, bushing three130 creates eight bundles of impregnated fibers that will be continuallycompressed through the series of next bushings.

The puller pulls the fibers through bushing three 130 to bushing four140. Bushing four 140 comprises the same configuration as bushing three130. Bushing four 140 comprises a square inner portion 141 having fourouter corner passageways 142 a, 142 b, 142 c and 142 d and four innerpassageways 144 a, 144 b, 144 c and 144 d. Preferably, the four outercorner passageways 142 a-d and the four inner passageways 144 a-d areslightly smaller in size than the similarly configured passageways inbushing three 130. Bushing four 140 compresses the fibers pulled throughbushing three.

The puller pulls the fibers from bushing four 140 to bushing five 150.Preferably, the four outer corner passageways 152 a, 152 b, 152 c and152 d and the four inner passageways 154 a, 154 b, 154 c and 154 d areslightly smaller in size than the similarly configured passageways inbushing four 140. Bushing five 150 compresses the fibers pulled throughbushing four 140.

For each of the successive bushings, each bushing creates a bundle offibers with an increasingly smaller diameter. Preferably, each smallerbushing wipes off excess resin to approach the optimal and desiredproportion of resin to fiber composition.

The puller pulls the fibers from bushing five 150 to bushing six 160.Preferably, the four outer corner passageways 162 a, 162 b, 162 c and162 d and the four inner passageways 164 a, 164 b, 164 c and 164 d areslightly smaller in size than the similarly configured passageways inbushing five 150. Bushing six 160 compresses the fibers pulled throughbushing five 150.

Bushing seven 170 comprises an inner square 171 having four outer cornerpassageways 172 a, 172 b, 172 c and 172 d and one inner passageway 174.The puller pulls the fibers from the four inner passageways 164 ofbushing six 160 through the single inner passageway 174 in bushing seven170. The process compacts the product to a final uniform concentriccore. Preferably, fibers are pulled through the outer four corners 172a, 172 b, 172 c, 172 d of bushing seven 170 simultaneous with compactingof the inner four passageways 164 from bushing six 160.

The puller pulls the fibers through bushing seven 170 to bushing eight180. The puller pulls the inner compacted core 184 and the outer fourcorners 182 a, 182 b, 182 c, 182 d migrate inwardly closer to the core184. Preferably, the outer fibers diminish the distance between theinner core and the outer corners by half the distance.

The puller pulls the fibers through bushing eight 180 to bushing nine190. Bushing nine 190 is the final bushing for the formation of thecomposite core. The puller pulls the four outer fiber bundles and thecompacted core through a passageway 192 in the center of bushing nine190.

Preferably, bushing nine 190 compacts the outer portion and the innerportion creating an inner portion of carbon and an outer portion ofglass fiber. FIG. 8 for example, illustrates a cross-section of acomposite cable. The example illustrates a composite core member 200having an inner reinforced carbon fiber composite portion 202 surroundedby an outer reinforced glass fiber composite portion 204.

Temperature is kept constant throughout zone 5. The temperature isdetermined by the process and is high enough to keep the resin in asemi-cured state. At the end of zone 5, the product comprises the finallevel of compaction and the final diameter.

The puller pulls the fibers from zone 5 to zone 6 a curing stagepreferably comprising an oven with constant heat and airflow as in zone5, 4 and 2. The oven uses the same constant heating and cross circularair flow as in zone 5, zone 4 and zone 2. The process determines thecuring heat. The curing heat remains constant throughout the curingprocess. In the present invention, the preferred temperature for curingranges from about 350° F. to about 400° F. The curing process preferablyspans within the range of about 8 to about 15 feet. More preferably, thecuring process spans about 10 feet in length. The high temperature ofzone 6 results in a final cure forming a hard resin.

Zone 6 may incorporate a bushing ten to assure that the final fibercomposite cor member holds its shape. In addition, another bushingprevents bluming of the core during curing.

During the next stages the composite core member product is pulledthrough a series of heating and cooling phases. The post cure heatingimproves cross linking within the resin matrix improving the physicalcharacteristics of the product. The pullers pull the fibers to zone 7, acooling device. Preferably, the mechanical configuration of the oven isthe same as in zones 2, 4, 5 and 6. More specifically, the devicecomprises a closed circular air system using a cooling device and ablower. Preferably, the cooling device comprises a plurality of coils.Alternatively, the coils may be horizontally structured consecutivecooling elements. In a further alternative, the cooling device comprisescooling spirals. The blower is placed upstream from the cooling deviceand continuously blows air in the cooling chamber in an upstreamdirection. The air circulates through the device in a closed circulardirection keeping the air throughout at a constant temperature.Preferably, the cooling temperature ranges from within about 40 to about180° F.

The pullers pull the composite member through zone 7 to zone 8, thepost-curing phase. The composite core member is heated to post-curingtemperature to improve the mechanical properties of the composite coremember product.

The pullers pull the composite core member through zone 8 to zone 9, thepost curing cooling phase. Once the composite core has been reheated,the composite core is cooled before the puller grabs the compactedcomposite core. Preferably, the composite core member cools for adistance ranging about 8 to about 15 feet by air convection beforereaching the puller. Most preferably, the cooling distance is about 10feet.

The pullers pull the composite core member through the zone 9 coolingphase into zone 10, a winding system whereby the fiber core is wrappedaround a wheel for storage. It is critical to the strength of the coremember that the winding does not over stress the core by bending. In oneembodiment, the core does not have any twist and can only bend a certaindegree. In another embodiment, the wheel has a diameter of seven feetand handles up to 6800 feet of B-stage formed composite core member. Thewheel is designed to accommodate the stiffness of the B-stage formedcomposite core member without forcing the core member into aconfiguration that is too tight. In a further embodiment, the windingsystem comprises a means for preventing the wheel from reversing flowfrom winding to unwinding. The means can be any device that prevents thewheel direction from reversing for example, a brake system.

In a further embodiment, the process includes a quality control systemcomprising a line inspection system. The quality control process assuresconsistent product. The quality control system may include ultrasonicinspection of composite core members; record the number of tows in theend product; monitor the quality of the resin; monitor the temperatureof the ovens and of the product during various phases; measureformation; measure speed of the pulling process. For example, each batchof composite core member has supporting data to keep the processperforming optimally. Alternatively, the quality control systemcomprises a marking system. The marking system wherein the markingsystem marks the composite core members with the product information ofthe particular lot. Further, the composite core members may be placed indifferent classes in accordance with specific qualities, for example,Class A is high grade, Class B and Class C.

The fibers used to process the composite core members can beinterchanged to meet specifications required by the final composite coremember product. For example, the process allows replacement of fibers ina composite core member having a carbon core and a glass fiber outercore with high grade carbon and E-glass. The process allows the use ofmore expensive better performing fibers in place of less expensivefibers due to the combination of fibers and the small core sizerequired. In one embodiment, the combination of fibers creates a highstrength inner core with minimal conductivity surrounded by a lowmodulus nonconductive outer insulating layer. In another embodiment, theouter insulating layer contributes to the flexibility of the compositecore member and enables the core member to be wound, stored andtransported.

Another embodiment of the invention, allows for redesign of thecomposite core cross section to accommodate varying physical propertiesand increase the flexibility of the composite core member. Referringagain to FIG. 5, the different composite shapes change the flexibilityof the composite core member. Changing the core design may enablewinding of the core on a smaller diameter wheel. Further, changing thecomposite core design may affect the stiffness and strength of the innercore. As an advantage, the core geometry may be designed to achieveoptimal physical characteristics desired in a final ACCC cable.

In another embodiment of the invention, the core diameter is greaterthan 0.375 inches. A core greater than 0.375 inches cannot bend toachieve a 7-foot wrapping diameter. The potential strength on theoutside bend shape exceeds the strength of the material and the materialwill crack. A core diameter of ½ to ⅝ inch may require a wheel diameterof 15 feet and this is not commercially viable. To increase theflexibility of the composite core, the core may be twisted or segmentedto achieve a wrapping diameter that is acceptable. One 360 degree twistof fiber orientation in the core for one revolution of core.Alternatively, the core can be a combination of twisted and straightfiber. The twist may be determined by the wheel diameter limit. If thelimit is prohibited then twist by one revolution of diameter of thewheel. The tension and compression stresses in the core are balanced byone revolution.

Winding stress is reduced by producing a segmented core. FIG. 5illustrates some examples of possible cross section configurations ofsegmented cores. The segmented core under the process is formed bycuring the section as separate pieces wherein the separate pieces arethen grouped together. Segmenting the core enables a composite memberproduct having a core greater than 0.375 inches to achieve a desirablewinding diameter without additional stress on the member product.

Variable geometry of the cross sections in the composite core membersare preferably processed as a multiple stream. The processing system isdesigned to accommodate formation of each segment in parallel.Preferably, each segment is formed by exchanging the series ofconsecutive bushings for bushings having predetermined configurationsfor each of the passageways. In particular, the size of the passagewaysmay be varied to accommodate more or less fiber, the arrangement ofpassageways may be varied in order to allow combining of the fibers in adifferent configuration in the end product and further bushings may beadded within the plurality of consecutive bushings to facilitateformation of the varied geometric cross sections in the composite coremember. At the end of the processing system the five sections in fivestreams of processing are combined at the end of the process to form thecomposite cable core. Alternatively, the segments may be twisted toincrease flexibility and facilitate winding The final composite core iswrapped in lightweight high conductivity aluminum forming a compositecable. Preferably, the composite core cable comprises an inner carboncore having an outer insulating glass fiber composite layer and twolayers of trapezoidal formed strands of aluminum.

In one embodiment, the inner layer of aluminum comprises a plurality oftrapezoidal shaped aluminum segments wrapped in a counter-clockwisedirection around the composite core member. Each trapezoidal section isdesigned to optimize the amount of aluminum and increase conductivity.The geometry of the trapezoidal segments allows for each segment to fittightly together and around the composite core member.

In a further embodiment, the outer layer of aluminum comprises aplurality of trapezoidal shaped aluminum segments wrapped in a clockwisedirection around the composite core member. The opposite direction ofwrapping prevents twisting of the final cable. Each trapezoidal aluminumelement fits tightly with the trapezoidal aluminum elements wrappedaround the inner aluminum layer. The tight fit optimizes the amount ofaluminum and decreases the aluminum required for high conductivity.

EXAMPLE

A particular embodiment of the invention is now described wherein thecomposite strength member comprises E-glass and carbon type 13 sizing.E-glass combines the desirable properties of good chemical and heatstability, and good electrical resistance with high strength. Thecross-sectional shape or profile is illustrated in FIG. 8 wherein thecomposite strength member comprises a concentric carbon coreencapsulated by a uniform layer of glass fiber composite. In a preferredembodiment the process produces a hybridized core member comprising twodifferent materials.

The fiber structures in this particular embodiment are 126 ends ofE-glass product, yield 900, Veterotex Amer and 16 ends of carbon ToraycaT7DOS yield 24K. The resin used is an epoxy resin called ARALDITE MY 721from Vantico.

In operation, the ends of 126 fiber tows of E-glass and 16 fiber tows ofcarbon are threaded through a fiber tow guide comprising two rows of 32passageways, two rows inner of 31 passageways and two innermost rows of4 passageways and into a preheating stage at 150° F. to evacuate anymoisture. After passing through the preheating oven, the fiber tows arepulled through a wet out tank. In the wet out tank a device effectuallymoves the fibers up and down in a vertical direction enabling thoroughwetting of the fiber tows. On the upstream side of the wet out tank islocated a wiper system that removes excess resin as the fiber tows arepulled from the tank. The excess resin is collected by a resin overflowtray and added back to the resin wet out tank.

The fiber tows are pulled from the wet out tank to a B-state oven thatsemi-cures the resin impregnated fiber tows to a tack stage. At thisstage the fiber tows can be further compacted and configured to theirfinal form in the next phase. The fiber tows are pulled to a next ovenat B-stage oven temperature to maintain the tack stage. Within the ovenare eight consecutive bushings that function to compact and configurethe fiber tows to the final composite core member form. Two fiber towends are threaded through each of the 134 passageways in the firstbushing which are machined to pre-calculated dimensions to achieve afiber volume of 72 percent and a resin volume of 28 percent in the finalcomposite core member. The ends of the fiber tows exiting frompassageways in the top right quarter comprising half of the two top rowsare threaded through passageways 132 of the next bushing; the ends ofthe fiber tows exiting from passageways in the top left quartercomprising half of the top two rows are threaded through passageway 136of the next bushing; the ends of the fiber tows exiting from passagewaysin the lower right quarter comprising half of the bottom two rows arethreaded through passageway 140 of the next bushing; the ends of thefiber tows exiting from passageways in the lower left quarter comprisinghalf of the bottom two rows are threaded through passageway 138 of thenext bushing; the right and left quarters of passageways in the middleupper row are threaded through passageways 142 and 144 of the nextbushing and the right and left quarters of passageways in the middlebottom row are threaded through passageways 134 and 146 respectively.

The fiber tows are pulled consecutively through the outer and innerpassageways of each successive bushing further compacting andconfiguring the fiber bundles. At bushing seven, the fiber bundlespulled through the inner four passageways of bushing six are combined toform a composite core whereas the remaining outer passageways continueto keep the four bundles glass fibers separate. The four outerpassageways of bushing seven are moved closer inward in bushing eight,closer to the inner carbon core. The fiber tows are combined with theinner carbon core in bushing nine forming a hybridized composite coremember comprising an inner carbon core having an outer glass layer.

The composite core member is pulled from the bushing nine to a finalcuring oven at an elevated temperature of 380° F. as required by thespecific resin. From the curing oven the composite core member is pulledthrough a cooling oven to be cooled to 150 to 180° F. After cooling thecomposite core member is pulled through a post curing oven at elevatedtemperature, preferably to heat the member to at least B-stagetemperature. After post-curing the member is cooled by air toapproximately 180° F. The member is cooled prior to grabbing by thecaterpillar puller to the core winding wheel having 6000 feet ofstorage.

EXAMPLE

An example of an ACCC reinforced cable in accordance with the presentinvention follows. An ACCC reinforced cable comprising four layers ofcomponents consisting of an inner carbon/epoxy layer, a nextglassfiber/epoxy layer and two layers of tetrahedral shaped aluminumstrands. The strength member consists of an advanced composite T700Scarbon/epoxy having a diameter of about 0.2165 inches, surrounded by anouter layer of R099-688 glassfiber/epoxy having a layer diameter ofabout 0.375 inches. The glassfiber/epoxy layer is surrounded by an innerlayer of nine trapezoidal shaped aluminum strands having a diameter ofabout 0.7415 inches and an outer layer of thirteen trapezoidal shapedaluminum strands having a diameter of about 1.1080 inches. The totalarea of carbon is about 0.037 in², of glass is about 0.074 in², of inneraluminum is about 0.315 in² and outer aluminum is about 0.5226 in². Thefiber to resin ratio in the inner carbon strength member is 70/30 byweight and the outer glass layer fiber to resin ratio is 75/25 byweight.

The specific specifications are summarized in the following table:

Glass Vetrotex roving R099-686 (900 Yield) Tensile Strength, psi 298,103Elongation at Failure, % 3.0 Tensile Modulus, × 10⁶ psi 11.2 GlassContent, % 57.2 Carbon (graphite) Carbon: Torayca T700S (Yield 24K)Tensile strength, Ksi 711 Tensile Modulus, Msi 33.4 Strain 2.1% Densitylbs/ft³ 0.065 Filament Diameter, in 2.8E−04 Epoxy Matrix System AralditeMY 721 Epoxy value, equ./kg 8.6-9.1 Epoxy Equivalent, g/equ. 109-Viscosity @ 50 C., cPs 3000-6000 Density @ 25 C. lb/gal. 1.1501.18Hardener 99-023 Viscosity @ 25 C., cPs  75-300 Density @ 25 C., lb/gal1.19-1/22 Accelerator DY 070 Viscosity @ 25 C., cPs <50 Density @ 25 C.,lb/gal 0.95-1.05

An ACCC reinforced cable having the above specifications is manufacturedaccording to the following. The process used to form the composite cablein the present example is illustrated in FIG. 1. First, 126 spools ofglass fiber tows 12 and 8 spools of carbon are set up in the rack system14 and the ends of the individual fiber tows 12, leading from spools 11,are threaded through a fiber tow guide 18. The fibers undergo tangentialpulling to prevent twisted fibers. A puller 16 at the end of theapparatus pulls the fibers through the apparatus. Each dispensing rack14 has a small brake to individually adjust the tension for each spool.The tows 12 are pulled through the guide 18 and into a preheating oven20 at 150° F. to evacuate moisture.

The tows 12 are pulled into wet out tank 22. Wet out tank 22 is filledwith an epoxy resin called ARALDITE MY 721 MY 721/Hardener99-023/Accelerator DY070 to impregnate the fiber tows 12. Excess resinis removed from the fiber tows 12 during wet out tank 22 exit. The fibertows 12 are pulled from the wet out tank 22 to a B-stage oven 24 and areheated to 200° F. Fiber tows 12 maintained separated by the guide 18,are pulled into a second B-stage oven 26 also at 200° F. comprising aplurality of consecutive bushings to compress and configure the tows 12.In the second B-stage oven 26, the fiber tows 12 are directed through aplurality of passageways provided by the bushings. The consecutivepassageways continually compress and configure the fiber tows 12 intothe final uniform composite core member.

The first bushing has two rows of 32 passageways, two inner rows of 31passageways each and two inner most rows of 4 passageways each. The 126glass fiber tows are pulled through the outer two rows of 32 and 31passageways, respectively. The carbon fiber tows are pulled through theinner two rows of 4 passageways eaten. The next bushing splits the toptwo rows in half and the left portion is pulled through the left upperand outer corner passageway in the second bushing. The right portion ispulled through the right upper and outer corner passageway in the secondbushing. The bottom two rows are split in half and the right portion ispulled through the lower right outer corner of the second bushing andthe left portion is pulled through the lower left outer corner of thesecond bushing. Similarly, the two inner rows of carbon are split inhalf and the fibers of the two right upper passageways are pulledthrough the inner upper right corner of the second bushing. The fibersof the left upper passageways are pulled through the inner upper leftcorner of the second bushing. The fibers of the right lower passagewaysare pulled through the inner lower right corner of the second bushingand the fibers of the left lower passageways are pulled through theinner lower left corner of the second bushing.

The fiber bundles are pulled through a series of seven bushingscontinually compressing and configuring the bundles into one hybridizeduniform concentric core member.

The composite core member is pulled from the second B-stage oven 26 to anext oven processing system 28 at 330 to 370° F. wherein the compositecore member is cured and pulled to a next cooling system 30 at 30 to100° F. for cooling. After cooling, the composite core is pulled to anext oven processing system 32 at 330 to 370° F. for post curing. Thepulling mechanism pulls the product through a 10 foot air cooling areaat about 180° F.

Nine trapezoidal shaped aluminum strands each having an area of about0.0350 or about 0.315 sq. in. total area on the core are wrapped aroundthe composite core after cooling. Next, thirteen trapezoidal shapedaluminum strands each strand having an area of about 0.0402 or about0.5226 sq. in. total area on the core are wrapped around the inneraluminum layer.

It is to be understood that the invention is not limited to the exactdetails of the construction, operation, exact materials, or embodimentsshown and described, as modifications and equivalents will be apparentto one skilled in the art without departing from the scope of theinvention.

1. A composite core for an electrical cable comprising: an inner corecomprising a plurality of substantially continuous reinforcing fibers ofat least a first type, the first fiber type having a tensile strengththat exceeds the tensile strength of glass fibers; an outer corecomprising a plurality of substantially continuous reinforcing fibers ofat least a second type, the second fiber type having a tensile strengthof or similar to glass fibers; and a resin matrix, wherein the fibers ofthe inner and the outer cores are embedded therein; wherein, the fibersof the inner core are different from the fibers of the outer core, andwherein the fibers of the inner and the outer cores are orientedsubstantially parallel to the longitudinal axis.
 2. A composite core asclaimed in claim 1 wherein, the first fiber type is carbon.
 3. Acomposite core as claimed in claim 1, wherein the second fiber type isglass.
 4. A composite core as claimed in claim 1 wherein, the firstreinforcing fiber type in the inner core comprises a modulus ofelasticity in the range of about 22 (151 GPa) to 37 Msi (255 GPa)coupled with a coefficient of thermal expansion in the range of about−0.7 to about 0 m/m/° C. and a tensile strength of at least about 350Ksi (2413 MPa) and the second reinforcing fiber type in the outer corecomprises a tensile strength in the range of at least about 180 Ksi(1241 MPa) coupled with a coefficient of thermal expansion in the rangeof about 5×10⁻⁶ to about 10×10⁻⁶ m/m/° C.
 5. A composite core as claimedin claim 1 wherein, the composite material of the inner core and theouter core is selected to meet physical characteristics in the endcomposite core including a tensile strength of at least 160 Ksi (1103MPa), a modulus of elasticity in the range of at least about 7 Msi (48GPa) to about 30 Msi (206 GPa), an operating temperature in the range ofabout 90 to about 230° C. and a thermal expansion coefficient at leastin the range of about 0 to about 6×10⁻⁶ m/m/° C.
 6. A composite core asclaimed in claim 1 comprising a fiber/resin volume fraction in the rangeof at least about 50%.
 7. A composite core as claimed in claim 1comprising a fiber/resin ratio of at least about 62% by weight.
 8. Acomposite core as claimed in claim 1 wherein, the inner core comprisescarbon fibers and the outer core comprises glass fibers.
 9. A compositecore as set forth in claim 1 wherein, said outer core and said innercore form a segmented concentric core.
 10. A composite core as claimedin claim 1 wherein, at least one layer of a plurality of aluminumsegments is wrapped around the core.
 11. A composite core for anelectrical cable comprising: a plurality of reinforcing fibers in athermosetting resin matrix to form the core, said core having at least50% fiber volume fraction, the plurality of reinforcing fibersconsisting of two or more different types of fibers, a first fiber typehaving a modulus of elasticity in the range of about 22 (151 GPa) to 37Msi (255 GPa) and a tensile strength at least about 350 Ksi (2413 MPa)and a second fiber type having a modulus of elasticity in the range ofabout 6 Msi to about 11.2 Msi and a tensile strength of at least about180 Ksi (1241 MPa); wherein, the fibers are arranged within the resinmatrix having the higher tensile strength fibers in the center of thecore.
 12. A composite core as claimed in claim 11 wherein, the firstreinforcing fiber type is carbon.
 13. A composite core as claimed inclaim 11 wherein, the second reinforcing fiber type is glass.
 14. Acomposite core as claimed in claim 11 wherein, the proportion and typeof fibers are selected to meet physical characteristics in the endcomposite core including a tensile strength in the range of at least 160Ksi (1103 MPa), a modulus of elasticity in the range of at least about 7(48 GPa) to about 30 Msi (206 GPa), an operating temperature in therange of about 90 to about 230° C. and a thermal expansion coefficientat least in the range of about 0 to about 6×10⁻⁶ m/m/° C.
 15. Acomposite core as claimed in claim 11 comprising a fiber resin ratio ofat least about 62% by weight.
 16. A composite core as claimed in claim11 wherein the first fiber type forms an inner core and the second fibertype forms an outer core that surrounds the inner core.
 17. A compositecore as claimed in claim 16 wherein, the inner core comprises carbonfibers and the outer core comprises glass fibers.
 18. A composite coreas set forth in claim 11 wherein, the core is segmented.
 19. A compositecore as claimed in claim 11 wherein, at least one layer of a pluralityof aluminum segments is wrapped around the core.
 20. A composite corefor an electrical cable comprising: an inner core consisting of aplurality of substantially continuous reinforcing fibers, the fibershaving a tensile strength that exceeds the tensile strength of glassfibers; an outer core surrounding the inner core consisting at least inpart of a plurality of substantially continuous reinforcing glassfibers; and a cured resin matrix, wherein the fibers of the inner andthe outer cores are embedded therein; wherein, the fibers of the innerand the outer cores are oriented substantially parallel to thelongitudinal axis.
 21. A composite core as claimed in claim 20 wherein,the fibers of the inner core are carbon.
 22. A composite core as claimedin claim 20 wherein, the inner core comprises carbon and basalt fibers.23. A composite core as claimed in claim 20 wherein, the fibers of theinner core have a modulus of elasticity in the range of about 22 toabout 37 Msi.
 24. A composite core as claimed in claim 20 comprising afiber/resin volume fraction in the range of at least about 50%.
 25. Acomposite core as claimed in claim 20 comprising a fiber resin ratio ofat least about 62% by weight.
 26. A composite core as claimed in claim20 wherein, at least one layer of a plurality of aluminum segments iswrapped around the core.
 27. A composite core for an electrical cablecomprising: an inner core comprising a plurality of reinforcing carbonfibers and at least a portion of a plurality of reinforcing fibershaving a tensile strength in excess of glass fibers; an outer coresurrounding the inner core comprising a plurality of glass fibers; and acured resin matrix, wherein the fibers of the inner and the outer coresare embedded therein; wherein, the fibers of the inner and outer coresare oriented substantially parallel to the longitudinal axis.
 28. Thecomposite core as claimed in claim 27, wherein the fiber having atensile strength in excess of glass fibers is basalt.
 29. An electricalcable comprising: a composite core further comprising: an inner corecomprising a plurality of substantially continuous reinforcing fibers ofat least a first type, the first type having a tensile strength thatexceeds the tensile strength of glass fibers, wherein the fibers aresubstantially parallel to the longitudinal axis; an outer corecomprising a plurality of substantially continuous reinforcing fibers ofat least a second type, the second type having a tensile strength of orsimilar to glass fibers, wherein the fibers are substantially parallelto the longitudinal axis; and a cured resin matrix, wherein the fibersof the inner and the outer cores are embedded therein; and at least onelayer of conductor surrounding said outer core.
 30. An electrical cableas claimed in claim 29 wherein, the composite material of the inner coreand the outer core is selected to meet physical characteristics in theend composite core including a tensile strength of at least 160 Ksi(1103 MPa), a modulus of elasticity in the range of at least about 7 Msi(48 GPa) to about 30 Msi (206 GPa), an operating temperature in therange of about 90 to about 230° C. and a thermal expansion coefficientat least in the range of about 0 to about 6×10⁻⁶ m/m/° C.
 31. Anelectrical cable as claimed in claim 29 wherein, the composite corecomprises a fiber/resin volume fraction in the range of at least about50%.
 32. An electrical cable as claimed in claim 29 wherein, thecomposite core comprises a fiber/resin ratio of at least about 62% byweight.
 33. An electrical cable as claimed in claim 29 wherein, thefibers of the inner core are carbon and the fibers of the outer core areglass.
 34. An electrical cable as claimed in claim 29 wherein, theconductor surrounding the core comprises a plurality of aluminumsegments.
 35. An electrical cable as set forth in claim 29 wherein, thecomposite core is segmented.
 36. A method of transmitting electricalpower comprising: using a cable comprising a composite core and at leastone layer of aluminum conductor surrounding the composite core, thecomposite core further comprising: an inner core comprising a pluralityof substantially continuous reinforcing fibers of at least a first type,the first type having a tensile strength that exceeds the tensilestrength of glass fibers, wherein the fibers are substantially parallelto the longitudinal axis; an outer core comprising a plurality ofsubstantially continuous reinforcing fibers of at least a second type,the second type having a tensile strength of or similar to glass fibers,wherein the fibers are substantially parallel to the longitudinal axis;and a cured resin matrix, wherein the fibers of the inner and the outercores are embedded therein; and transmitting power across the compositecable.